Tensioners are used to preload power transmission belts. The belts are used on belt drive systems on vehicle engines, for example, to power accessories or to drive camshafts.
Once installed the damping rate for tensioners is not adjustable. The damping rate, or coefficient, is a function of the damping material and the normal force exerted by a spring upon the damping material. During operation the damping material by its nature is worn away which can change the damping characteristics of the tensioner. Since the damping mechanisms are not adjustable the change in damping can result in adverse operating conditions, including excessive oscillations or tensioner failure.
Representative of the art is U.S. Pat. No. 6,575,860 to Dutil (2003) which discloses a belt tensioner for a power transmission belt system includes: (a) a base housing having a pivot shaft extending therefrom; (b) a tension arm pivotally mounted on the pivot shaft at a proximal end thereof, the proximal end of the tension arm including a rub surface and the distal end of the tension arm adapted to contact a power transmission belt; (c) a torsion spring operatively coupled between the base housing and the tension arm and adapted to bias the distal end of the tension arm against the power transmission belt; and (d) a damper assembly coupled to the housing, the damper assembly including: (1) a body of friction material that includes a friction surface adjacent to and facing the rub surface of the tension arm and (2) a damper spring integral with the body of friction material and biasing the body of friction material and associated friction surface against the rub surface of the tension arm.
What is needed is a tensioner comprising an instantaneously adjustable damping mechanism comprising a Belleville spring. The present invention meets this need.